Light scattering by selected zooplankton from the Gulf of Aqaba.

Light scattering by zooplankton was investigated as a major factor undermining transparency camouflage in these pelagic animals. Zooplankton of differing transparencies--including the hyperiid amphipod Anchylomera blossevillei, an unknown gammarid amphipod species, the brine shrimp Artemia salina, the euphausiid shrimp Euphausia diomedeae, the isopod Gnathia sp., the copepods Pontella karachiensis, Rhincalanus sp. and Sapphirina sp., the chaetognath Sagitta elegans and an enteropneust tornaria larva--were illuminated dorsally with white light (400-700 nm). Spectral measurements of direct transmittance as well as relative scattered radiances at angles of 30 degrees , 90 degrees , 150 degrees and 180 degrees from the light source were taken. The animals sampled had transparencies between 1.5% and 75%. For all species, the highest recorded relative scattered radiance was at 30 degrees , with radiances reaching 38% of the incident radiance for the amphipod A. blossevillei. Scattering patterns were also found to be species-specific for most animals. Relative scattered radiances were used to estimate sighting distances at different depths. These calculations predict that all of the examined zooplankton are brighter than the background radiance when viewed horizontally, or from diagonally above or below at shallow depths. Thus, in contrast to greater depths, the best strategy for detecting transparent zooplankton in the epipelagic environment may be to search for them from above while looking diagonally downwards, looking horizontally or looking from below diagonally upwards. Looking directly upwards proved to be more beneficial than the other viewing angles only when the viewed animal was at depths greater than 40 m.

Cost-effectiveness in Canada of intravenous proton pump inhibitors for all patients presenting with acute upper gastrointestinal bleeding.

BACKGROUND: The administration of proton pump inhibitors intravenously after endoscopic treatment of peptic ulcers significantly reduces the recurrence of bleeding. AIM: To evaluate the incremental cost-effectiveness in Canada of intravenous proton pump inhibitor before endoscopic therapy to patients presenting with acute upper gastrointestinal bleeding, compared with endoscopic treatment alone. METHODS: From a third-party payer perspective, we modelled the costs and effectiveness over 60 days of the two approaches using decision analysis. The probabilities of various outcomes, such as re-bleeding and the need for surgery, were taken from the published literature. We included the costs of intravenous proton pump inhibitor, therapeutic endoscopy, surgical procedures and hospitalizations, all expressed in 2001 Canadian dollars. RESULTS: In a hypothetical cohort of 1000 patients, the intravenous proton pump inhibitor approach resulted in mean savings of 20,700 Canadian dollars with 37 re-bleeding episodes averted. The investigation of uncertainty resulted in a likelihood of intravenous proton pump inhibitor being cost-effective of at least 0.73. CONCLUSION: It is common in Canada to administer intravenous proton pump inhibitors to patients with upper gastrointestinal bleeding even before endoscopic confirmation of bleeding peptic ulcers. Our results suggest that this approach has a high likelihood of being cost-effective.

Using economic evaluations to make formulary coverage decisions. So much for guidelines.

BACKGROUND: It is mandatory for drug manufacturers requesting formulary inclusion under the British Columbia (BC) provincial drug plan to submit a pharmacoeconomic analysis according to published guidelines. These submissions are reviewed by the Pharmacoeconomic Initiative (PI) of BC. OBJECTIVE: To assess the compliance of submitted studies with specific criteria outlined in the guidelines, to assess the methodological quality of individual submissions, and to demonstrate the importance of submitting guidelines-compliant pharmacoeconomic analyses. DATA AND METHODS: All submissions between January 1996 and April 1999 assessed by the PI of BC were included. Submissions were reviewed according to a checklist to establish compliance with respect to choice of comparator drug, study perspective, sensitivity analysis, analytical horizon and discounting. Submissions were examined for association between analytical technique and author, and between source of submission and compliance. Association between compliance and recommendation for approval was also examined. RESULTS: 95 applications were reviewed. Seven submitted no analyses. There were 25 cost-comparison/consequence, 14 cost-effectiveness, 11 cost-minimisation, 9 cost-utility/benefit and 29 budget-impact analyses. 65 of these 88 submissions failed to comply with guidelines. Of these, 45% used an inappropriate comparator drug, 61% lacked a sensitivity analysis, 73% used a third-party payer and excluded a societal perspective, 66% did not provide a long term evaluation and 25% did not specify any time horizon. 80% of noncompliant studies were cost-comparison/consequence or budget-impact analyses (p < 0.001, Fisher's Exact). Of 25 cost-comparison/consequence and 29 budget-impact analyses, 19 (76%) and 24 (83%), respectively, were industry-conducted, whereas cost-effectiveness (11 of 14) and cost-utility/benefit (6 of 9) analyses were mostly subcontracted to private consultants or academics (p < 0.001, Fisher's Exact). 74% of all submissions (compliant and noncompliant) were not recommended by the PI for listing as a provincial drug plan benefit, 16% received approval for restricted benefit and 9% were recommended as full benefit. 80% of the noncompliant submissions were not recommended (p = 0.06, Fisher's Exact test). Moreover, a strong association between type of analysis and type of recommendation was found (p = 0.03, Fisher's Exact test). Cost-comparison/consequence and budget-impact analyses were less likely to be recommended. IMPLICATIONS OF FINDINGS: Our findings show poor compliance with guidelines, especially among industry-conducted studies. Possible explanations are lack of expertise in pharmacoeconomics and/or scepticism regarding the importance of guidelines and submission quality in decision making. As corroborated by the strong associations between type of recommendation and compliance, and between type of recommendation and type of analysis, these 2 characteristics have a significant impact on decision making.

Co-transcription of Rhizobium meliloti lysyl-tRNA synthetase and glutamyl-tRNA synthetase genes.

An open reading frame encoding a putative polypeptide very similar to several lysyl-tRNA synthetases was found 10 nucleotides downstream of Rhizobium meliloti gltX encoding glutamyl-tRNA synthetase. Expression of this gene complemented a mutation in lysS of Escherichia coli and led to the overexpression of a polypeptide of the expected mass (62 kDa), thus confirming that it encodes R. meliloti lysyl-tRNA synthetase. Reverse transcription/polymerase chain reaction was used to demonstrate that this lysS gene is co-transcribed with gltX in R. meliloti. This is the first reported case of two immediately adjacent and co-transcribed genes encoding aminoacyl-tRNA synthetases.

A single dose of an effective whole cell pertussis vaccine does not significantly increase protection in children primed with a less effective vaccine.

We evaluated if a single dose of a protective whole cell pertussis vaccine given before school entry to children primed with a less effective vaccine would increase their protection. A school cohort including 3876 students and a family cohort including 162 children were assessed. Although there was a trend toward increased protection. the better vaccine did not provide a significant improvement. These results suggest that a single dose of an effective vaccine given to children primed with a less effective one does not raise the protection to at level similar to that provided by three doses of the better vaccine.

Expression of human dystrophin following the transplantation of genetically modified mdx myoblasts.

Transplantation of genetically modified autologous myoblasts has been proposed as a possible solution to avoid long-term use of immunosuppressive drugs. To determine the conditions to be used in this kind of approach for possible treatment of dystrophin deficiency, mdx myoblasts were infected at different multiplicities of infection (MOI or 0.01-1000) with an adenoviral vector containing a CMV promoter/enhancer driven 6.3 kb human dystrophin cDNA (minigene) and tested in vitro for transgene expression. In these cultures, dystrophin mRNA was found to be proportionate with increasing MOI. Primary myoblast cultures derived from transgenic mdx mice expressing beta-Gal under a muscle-specific promoter and showing high expression of the human mini-dystrophin transgene introduced by the adenoviral vector were grafted into anterior tibialis muscles of SCID mice. Ten and 24 days after transplantation, numerous muscle fibers expressing both human dystrophin and beta-Gal were detected throughout the mouse muscles by immunohistochemistry using an antibody specific for human dystrophin. The presence of the human mini-dystrophin mRNA was also detected by RT-PCR. These results demonstrate that three essential conditions in autologous myoblast transplantation can be achieved: (1) in vivo survival of at least some of the transduced myoblasts; (2) efficient fusion of these cells with the host muscle fibers; and (3) the high expression of the dystrophin transgene in situ. Furthermore, this article provides a novel RT-PCR-based technique to quantify the human dystrophin minigene expression in vitro and in vivo.

Adaptation of parathyroid function to intravenous 1,25-dihydroxyvitamin D3 or partial parathyroidectomy in normal dogs.

Parathyroid function was studied in 14 normal dogs 1 month before and after daily i.v. administration of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) (eight dogs), or about 50% parathyroidectomy (six dogs), to test the hypothesis that degradation of newly synthesized intact parathyroid hormone (I-PTH) is involved in parathyroid gland adjustment to a modified demand for I-PTH. Parathyroid function was studied through i.v. infusions of Na2EDTA and CaCl2 and measurement of ionized calcium (Ca2+), I-PTH and carboxyl-terminal PTH (C-PTH) at various time points. The C-PTH/I-PTH ratio was used as an index for change in the relative proportion of circulating C-PTH vs I-PTH, 1 month prior to and following each intervention. This ratio was further validated by looking at the HPLC profile of I- and C-PTH in hypo- and hypercalcemia under experimental conditions. Basal Ca2+ was unaltered 1 month after surgery, and was maintained constant in the 1,25-(OH)2D3-treated group by gradually decreasing 1,25-(OH)2D3 doses over time from 0.25 to 0.13 microgram twice daily during the last week of the experimental protocol. In this same group, basal 1,25-(OH)2D3 was increased by 65% (P < 0.0001) and basal I-PTH was decreased by 40% (P < 0.05), while basal C-PTH and the C-PTH/I-PTH ratio remained unchanged. Stimulated and non-suppressible I- and C-PTH followed the same pattern with, this time, an increase of stimulated and non-suppressible C-PTH/I-PTH ratio of 60% (P < 0.05) and 85% (P < 0.05) respectively. There was no change in basal I-PTH, C-PTH, or C-PTH/I-PTH ratio after surgery. However, stimulated I- and C-PTH were decreased by 45% (P < 0.005) and 65% (P < 0.005) respectively, with a 30% (P < 0.005) decrease of stimulated C-PTH/I-PTH ratio. There was no change in non-suppressible I-PTH, while non-suppressible C-PTH decreased by 55% (P < 0.005), with a 55% (P < 0.05) decrease in non-suppressible C-PTH/I-PTH ratio. The HPLC profiles of I- and C-PTH obtained in hypo- and hypercalcemia disclosed a similar distribution of the immuno-reactivity into peaks before and after i.v. administration of 1,25-(OH)2D3 as well as partial parathyroidectomy. This indicated that C-PTH/I-PTH ratio changes were related to different circulating levels of I- and C-PTH rather than to a different composition of I- and C-PTH. These data indicate a shift in the circulating PTH profile toward more PTH carboxyl-terminal fragments after 1 month of i.v. 1,25-(OH)2D3, but toward more intact PTH 1 month after about 50% parathyroidectomy, possibly reflecting adjustments in PTH degradation induced by a modified demand for I-PTH. Although these changes are most likely modulated at the parathyroid gland level, we cannot formally eliminate participation of the hormone's peripheral metabolism.

Widespread use of the glu-tRNAGln transamidation pathway among bacteria. A member of the alpha purple bacteria lacks glutaminyl-trna synthetase.

The expression of the Rhizobium meliloti glutamyl-tRNA synthetase gene in Escherichia coli under the control of a trc promoter results in a toxic effect upon isopropyl-beta-D-thiogalactopyranoside induction, which is probably caused by a misacylation activity. To further investigate this unexpected result, we looked at the pathway of Gln-tRNAGln formation in R. meliloti. No glutaminyl-tRNA synthetase activity has been found in R. meliloti crude extract, but we detected a specific aminotransferase activity that changes Glu-tRNAGln to Gln-tRNAGln. Our results show that R. meliloti, a member of the alpha-subdivision of the purple bacteria, is the first Gram-negative bacteria reported to use a transamidation pathway for Gln-tRNAGln synthesis. A phylogenetic analysis of the contemporary glutamyl-tRNA synthetase and glutaminyl-tRNA synthetase amino acid sequences reveals that a close evolutionary relationship exists between R. meliloti and yeast mitochondrial glutamyl-tRNA synthetases, which is consistent with an origin of mitochondria in the alpha-subdivision of Gram-negative purple bacteria. A 256-amino acid open reading frame closely related to bacterial glutamyl-tRNA synthetases, which probably originates from a glutamyl-tRNA synthetase gene duplication, was found in the 4-min region of the E. coli chromosome. We suggest that this open reading frame is a relic of an ancient transamidation pathway that occurred in an E. coli ancestor before the horizontal transfer of a eukaryotic glutaminyl-tRNA synthetase (Lamour, V., Quevillon, S., Diriong, S., N'Guyen, V. C., Lipinski, M., and Mirande, M.(1994) Proc. Natl. Acad. Sci. U. S. A. 91, 8670-8674) and that it favored its stable acquisition. From these observations, a revisited model for the evolution of the contemporary glutamyl-tRNA synthetases and glutaminyl-tRNA synthetases that differs from the generally accepted model for the evolution of aminoacyl-tRNA synthetases is proposed.

The zinc-binding site of Escherichia coli glutamyl-tRNA synthetase is located in the acceptor-binding domain. Studies by extended x-ray absorption fine structure, molecular modeling, and site-directed mutagenesis.

The zinc contents of fragments of Escherichia coli glutamyl-tRNA synthetase, as well as the conservation of the CYC sequence only in zinc-containing glutamyl-tRNA synthetases, suggested that the 98CYCX24-CRHSHEHHADDEPC138 includes some or all residues involved in binding its zinc atom (Liu, J., Lin, S.-X., Blochet, J.-E., Pézolet, M., and Lapointe, J. (1993) Biochemistry 32, 11390-11396). Extended x-ray absorption fine structure (EXAFS) shows that this zinc atom has a four-coordinate non-planar coordination environment with 3 sulfur and 1 nitrogen atoms with bond lengths, respectively, 2.37 +/- 0.02 A and 2.01 +/- 0.02 A, presumably belonging to 3 cysteine residues and 1 histidine residue. Conservative replacement of each histidine and cysteine residue of the 98C-138C segment, respectively, with glutamine (Q) and serine (S), yields variants H129Q, H131Q, H132Q, and C138S (which sustain the growth at 42 degrees C of E. coli JP1449, whose glutamyl-tRNA synthetase is thermosensitive) and C98S, C100S, C125S, and H127Q (which do not). The amount of this enzyme in these mutants is at least 1 order of magnitude larger than that in a wild type strain; however, no glutamyl-tRNA synthetase activity is detectable in extracts of the variants C100S and C125S, whereas its specific activity in those of C98S and H127Q is about 10-fold lower than in cells overproducing the wild type enzyme or the variants H129Q, H131Q, H132Q, and C138S. These results indicate that the zinc atom present in E. coli glutamyl-tRNA synthetase is bound by the 2 evolutionarily conserved cysteines at positions 98 and 100, and by Cys125 and His127. Molecular modeling of the N-terminal half of this enzyme, using the known structure of E. coli glutaminyl-tRNA synthetase, supports this conclusion and suggests that the 98C-127H segment does not have the characteristics of the classical zinc fingers.

Clustering and co-transcription of the Bacillus subtilis genes encoding the aminoacyl-tRNA synthetases specific for glutamate and for cysteine and the first enzyme for cysteine biosynthesis.

The Bacillus subtilis cysE and cysS genes encoding, respectively, the serine acetyltransferase and the cysteinyl-tRNA synthetase were found downstream from the gltX gene encoding the glutamyl-tRNA synthetase. This gene organization is also conserved in Bacillus stearothermophilus where the cysE and cysS genes show high amino acid identity with those of B. subtilis. In both organisms the coding sequences of cysE and cysS overlap, suggesting a translational coupling. B. subtilis cysE and cysS were expressed in Escherichia coli using the inducible trc promoter; they functionally complement mutants of E. coli affected in those genes. Overproduction of B. subtilis CysRS in E. coli has a toxic effect on cell growth. Disruption of gltX and cysS by Campbell-type insertion is lethal for the cell, indicating that these genes code for an essential and unique function in B. subtilis. S1 mapping analysis shows that the transcription of gltX is under the control of a sigma A promoter located 43 base pairs upstream of the initiation codon. A T-box sequence and a rho-independent terminator known to regulate expression of other aminoacyl-tRNA synthetase genes and of some amino acid biosynthetic operons in Bacillus sp., were found between gltX and cysE. No sigma A promoter was detected upstream of cysE, which is consistent with the lethality of a Campbell-type insertion using a plasmid that interrupts transcription coming from the gltX promoter, and suggests that gltX, cysE, and cysS constitute an operon. This is the first case where genes implicated in the biosynthesis of an amino acid and its cognate aminoacyl-tRNA synthetase are shown to be co-transcribed.

Ovarian metastases of breast carcinoma. A clinicopathologic study of 59 cases.

Of 165 ovarian metastases recorded in the files of L'Hôtel-Dieu de Québec, Canada, between 1951 and 1987, 64 (38%) were from breast adenocarcinomas. Histopathologic material was available in 59 instances, of which 22 were autopsy cases and 28 were incidental findings at therapeutic oophorectomy. The patients' ages ranged from 25 to 80 years (average, 48.6 years). Sixty-four percent of the metastases were bilateral and 36% were unilateral. An ovarian metastasis was detected before the breast cancer in only one instance. The median interval between the diagnosis of breast carcinoma and the ovarian metastasis was 11.5 months and was related to the initial stage of the breast disease. The median survival after the diagnosis of ovarian metastasis was 16 months. The ovaries were grossly normal in 27 (46%) cases and 18 (31%) metastases were less than 1 mm in diameter. The size of the metastases was not related to the interval after the diagnosis of the breast carcinoma and did not influence the outcome of the patients. Forty-four metastases (75%) showed an indian file or ductal patterns easily identifiable as metastases of breast origin. The remaining cases presented various histologic features mimicking primary ovarian tumors or tumor-like conditions such as stromal luteoma, hyperthecosis, dysgerminoma, granulosa cell tumor, and carcinoid tumor. No metastasis had features of Krukenberg tumor. The authors conclude that metastases from breast cancer are generally small and are the reflection of an advanced disease. A metastasis of breast origin can be suspected histologically in most cases.

Cloning and sequencing of the gltX gene, encoding the glutamyl-tRNA synthetase of Rhizobium meliloti A2.

The gltX gene, coding for the glutamyl-tRNA synthetase of Rhizobium meliloti A2, was cloned by using as probe a synthetic oligonucleotide corresponding to the amino acid sequence of a segment of the glutamyl-tRNA synthetase. The codons chosen for this 42-mer were those most frequently used in a set of R. meliloti genes. DNA sequence analysis revealed an open reading frame of 484 codons, encoding a polypeptide of Mr 54,166 containing the amino acid sequences of an NH2-terminal and various internal fragments of the enzyme. Compared with the amino acid sequence of the glutamyl-tRNA synthetase of Escherichia coli, the N-terminal third of the R. meliloti enzyme was strongly conserved (52% identity); the second third was moderately conserved (38% identity) and included a few highly conserved segments, whereas no significant similarity was found in the C-terminal third. These results suggest that the C-terminal part of the protein is probably not involved in the recognition of substrates, a feature shared with other aminoacyl-tRNA synthetases.

The virgin, modified, human, umbilical vein graft: morphologic characteristics and mechanical properties.

The authors used macrophotography, endoscopy, roentgenography, light microscopy, and transmission and scanning electron microscopy to assess the morphologic characteristics of 37 virgin, human, umbilical vein grafts. The specimens showed deep longitudinal folds (22%) and multiple transverse folds of the intimal surface (27%), irregularity of wall thickness (41%) and intimal breakdown exposing thrombogenic layers of the vein wall to blood (19%). The mechanical properties also studied were dynamic compliance, Young's modulus, breaking strength and breaking strain. The mean dynamic compliance was 6.44 X 10(-4) mm Hg-1 (SD = 2.02 X 10(-4) mm Hg-1, i.e., 31%), which is in agreement with results of others. The specimens showed great variability in Young's modulus, breaking strength and breaking strain. The structural deficiencies and variable mechanical properties of human umbilical vein grafts require investigation to determine their effect on patency rates due to increased thrombogenicity and thus to establish whether there are potential hazards associated with their use.

Pathologic features of surgically excised human umbilical vein grafts.

This article describes the pathologic changes in 31 human umbilical vein grafts excised from 23 patients after implantations ranging from 24 hours to 5 years. Gross morphologic examination, light microscopy, and scanning electron microscopy demonstrated that the umbilical vein grafts appeared to be fragile and easily delaminated. Bacteremic colonization on the luminal surface was present in the grafts removed because of infections but in two instances had extended into the wall. The presence of lipid on the surface and in the subintimal layer was observed in five grafts, three of which had been implanted for less than 1 month. We concluded that human umbilical vein grafts pathologically exhibit fragility, biodegradation, lipid accumulation, and bacterial colonization in infected cases, and these characteristics may adversely affect the durability and long-term success of the prosthesis.

Recovery of acrylonitrile from charcoal tubes at low levels.

Data are presented for the recovery of acrylonitrile from charcoal tubes at levels lower than those tested in NIOSH Method S156. A 2% by volume acetone in CS2 solution is used as desorbing solvent. An injection volume of 2 muL and a 3-m long by 3.2-mm o.d. (10-ft x 1/8-in) stainless steel column filled with 20% SP-1000 on 80/100 Supelcoport gives adequate resolution of the acrylonitrile. Results indicate that recoveries are adequate for sample sizes which correspond to a 15-liter sample at 0.5 and 0.25 ppm, and that acrylonitrile collected on carbon in the absence of inhibitor is stable for at least a week.